using System;
using System.IO;

namespace SharpCompress.IO;

public class RewindableStream : Stream
{
    private readonly Stream stream;
    private MemoryStream bufferStream = new MemoryStream();
    private bool isRewound;
    private bool isDisposed;

    public RewindableStream(Stream stream) => this.stream = stream;

    internal bool IsRecording { get; private set; }

    protected override void Dispose(bool disposing)
    {
        if (isDisposed)
        {
            return;
        }
        isDisposed = true;
        base.Dispose(disposing);
        if (disposing)
        {
            stream.Dispose();
        }
    }

    public void Rewind(bool stopRecording)
    {
        isRewound = true;
        IsRecording = !stopRecording;
        bufferStream.Position = 0;
    }

    public void Rewind(MemoryStream buffer)
    {
        if (bufferStream.Position >= buffer.Length)
        {
            bufferStream.Position -= buffer.Length;
        }
        else
        {
            bufferStream.TransferTo(buffer);
            //create new memorystream to allow proper resizing as memorystream could be a user provided buffer
            //https://github.com/adamhathcock/sharpcompress/issues/306
            bufferStream = new MemoryStream();
            buffer.Position = 0;
            buffer.TransferTo(bufferStream);
            bufferStream.Position = 0;
        }
        isRewound = true;
    }

    public void StartRecording()
    {
        //if (isRewound && bufferStream.Position != 0)
        //   throw new System.NotImplementedException();
        if (bufferStream.Position != 0)
        {
            var data = bufferStream.ToArray();
            var position = bufferStream.Position;
            bufferStream.SetLength(0);
            bufferStream.Write(data, (int)position, data.Length - (int)position);
            bufferStream.Position = 0;
        }
        IsRecording = true;
    }

    public override bool CanRead => true;

    public override bool CanSeek => stream.CanSeek;

    public override bool CanWrite => false;

    public override void Flush() => throw new NotSupportedException();

    public override long Length => stream.Length;

    public override long Position
    {
        get => stream.Position + bufferStream.Position - bufferStream.Length;
        set
        {
            if (!isRewound)
            {
                stream.Position = value;
            }
            else if (value < stream.Position - bufferStream.Length || value >= stream.Position)
            {
                stream.Position = value;
                isRewound = false;
                bufferStream.SetLength(0);
            }
            else
            {
                bufferStream.Position = value - stream.Position + bufferStream.Length;
            }
        }
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        //don't actually read if we don't really want to read anything
        //currently a network stream bug on Windows for .NET Core
        if (count == 0)
        {
            return 0;
        }
        int read;
        if (isRewound && bufferStream.Position != bufferStream.Length)
        {
            // don't read more than left
            var readCount = Math.Min(count, (int)(bufferStream.Length - bufferStream.Position));
            read = bufferStream.Read(buffer, offset, readCount);
            if (read < readCount)
            {
                var tempRead = stream.Read(buffer, offset + read, count - read);
                if (IsRecording)
                {
                    bufferStream.Write(buffer, offset + read, tempRead);
                }
                read += tempRead;
            }
            if (bufferStream.Position == bufferStream.Length && !IsRecording)
            {
                isRewound = false;
                bufferStream.SetLength(0);
            }
            return read;
        }

        read = stream.Read(buffer, offset, count);
        if (IsRecording)
        {
            bufferStream.Write(buffer, offset, read);
        }
        return read;
    }

    public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();

    public override void SetLength(long value) => throw new NotSupportedException();

    public override void Write(byte[] buffer, int offset, int count) =>
        throw new NotSupportedException();
}
